The present invention relates to a lighting system for a motor vehicle. The system includes a laser light source for emitting a primary light beam of laser beams within a solid angle region around a beam direction, an element for photoluminescence, an optical element to convert the light beams of a secondary light into an emission light distribution; and a protective device to protect against laser rays leaking from the system. The element for photoluminescence is disposed within the primary light beam emitted from the laser light source and configured to absorb and scatter the laser beams impinging on the element and to emit a secondary light by means of photoluminescence and scattering.
Lighting arrangements for a motor vehicle lighting system of the prior art are provided with at least one laser light source. Since laser light sources, at high radiation intensities have a small surface emitting light and in essence radiate a collimated light beam, laser light operated optical systems having a small focal length can be configured for heavily bundled beams. Such systems thus require a small space and/or produce a more heavily collimated light beam.
Conventional laser light sources emit monochromatic light or light of a very limited wave length range, for example blue light. However, a motor vehicle headlight should emit mixed white light. For that, the blue light is to be converted into white light, wherein conversion of blue light of the laser light source into while mixed light uses phosphorescent substances or luminescent material. The combination of ceramic material and phosphorescent substances are termed photo luminescent converters. The photo luminescent converters include mostly a photo luminescent dye which is excited by the blue light from the laser source.
The photo luminescent dye emits light which differs in wave length from blue light, so that a portion of the irradiated light of a wave length range is converted into light of another wave length range. A further portion of the irradiated light is scatted by the photo luminescent converter. The scattered light and the light radiating by photo luminescence are superposed and lead for example to the desired white mixed light, which corresponds to the secondary light.
The coherent and heavily collimated light emitted from the laser source can be dangerous for the human eye, in particular at high radiation intensities. In motor vehicles, the laser sources should comply with certain security regulation; for example the intensity of light emitted from the headlight of a motor vehicle has to have a limit value to avoid blinding other drivers. These security requirements must be followed, especially when the headlights, due to the mechanical impact of an accident have been damaged, bent or moved from its original position or have been improperly mounted.
When using photo luminescence conversion in a motor vehicle headlight having a laser light source, photo luminescence conversion takes over security functions. Upon positional change or destruction of the converter heavily focused dangerous laser rays can be emitted from the headlight which is dangerous to the human eye, so that such emission should be avoided.
From DE 10 2010 220 476 A1, a lighting device for motor vehicle is known having a laser light source for emitting a primary light beam and a photo luminescence element. The photo luminescence element is disposed in such a way that the primary light beam emitted from the laser light source impinge on the photo luminescence element such that by exploiting photoluminescence by the impinging primary light beam a secondary light distribution is emitted. Present is also a temperature measuring apparatus to determine the temperature of the photoluminescence element and to monitor the normal operation of the lighting device.
The prior art also includes lighting systems for motor vehicles with a laser light source that include photo sensors to determine the composition of the emitted light. For example, it is possible to distinguish blue light from white mixed light and also a faulty functioning of the device, in particular, with respect to the photoluminescence converter.
WO 2014/072227 also describes a motor vehicle lighting device with a laser light source for radiating a primary light beam in a primary solid angle range around a primary radiation direction. The lighting device includes a photo luminescence element arranged in such a way that the primary light beam from the laser light source impinges on the photo luminescence element. The photo luminescence element is configured such that by exploiting photo luminescence by the impinging primary light beam, a secondary light distribution, especially polychromatic or white light is emitted. In addition, a radiation optical device can transform the secondary light distribution into a radiation light distribution of the lighting device. The lighting device includes a radiation suspension means in order to inhibit the transformation of light beams into the radiation light distribution, which, starting from the laser light source in the solid angle range, extends around the primary radiation direction.
One aspect of the present invention is to provide a lighting system for a motor vehicle with a laser light source where emission of heavily focused laser beams that are dangerous to the human eye, is prevented. The device should be a simple construction with a minimal amount of components at minimal space requirement. In addition, the cost of production, the maintenance and the installation should likewise be at a minimal level.
It would therefore be desirable and advantageous to provide an improved lighting system for motor vehicles to obviate prior art shortcomings and to reduce danger to the human eye that happens at high radiation intensities from laser light.